Size Distribution of Dispersed Luteal Cells During Oestrous Cycle in Angora Goats

The present study examines the size distribution of the goat steroidogenic luteal cells throughout the oestrous cycle. Corpora lutea (CL) were collected after laparatomy on days 5, 10 and 16 of the oestrous cycle. Luteal cells were isolated from CL by collagenase digestion. Steriodogenic luteal cells were identified by staining of the cells for 3beta-hydroxysteroid dehydrogenase activity, a marker for steroidogenic cells. Luteal cells having steroidogenic capacity covered a wide spectrum of sizes, ranging from 5 to 37.5 microm in diameter. There was a significant increase in mean cell diameters (p < 0.01) as CL aged. The mean cell diameter on day 5 was 11.55 +/- 0.12 microm, which was significantly increased and reached up to 19.18 +/- 0.24 mum by day 16 of the oestrous cycle. The ratio of large to small luteal cells was 0.06:1.0 on day 5 of the oestrous cycle. This ratio increased to 0.78:1.0 by day 16 of the oestrous cycle. Luteal cell size on days 5, 10 and 16 of the oestrous cycle reached its maximum at 7.5, 10 and 35 microm in diameter, respectively. Development of CL is associated with an increase in luteal cell size in goats. It is likely that small luteal cells could develop into large luteal cells as CL becomes older during oestrous cycle in goats.     

Plasma Progesterone in Gilts During the Prepuberal Period and the First Oestrous Cycle

The progesterone concentration of peripheral plasma in pigs has previously been studied during the oestrous cycle and in early pregnancy (Tillson & Erb 1967, Stabenfeldt et al 1969). The present study was undertaken to obtain some information on the concentration of plasma progesterone during the prepuberal period and during the first oestrous cycle in the pig.     

Effect of Complex Vertebral Malformation on Luteal Function in Holstein Cows During Oestrous Cycle and Early Pregnancy

The reason why cows carrying the mutation of complex vertebral malformation (CVM) show poor reproductive capability although they carry only one mutant allele is still not fully understood. Monitoring the progesterone profiles during oestrous cycle and early pregnancy in carrier cows might help explain their lowered reproductive capability. Progesterone concentration was measured in 19 CVM carrier cows and 21 control cows during oestrous cycle and early pregnancy. Milk samples were collected from all cows starting on the day of artificial insemination until day 45 post‐AI. Progesterone was measured in skim milk using enzyme‐linked immunosorbent assay (ELISA). Progesterone concentration was significantly reduced on day 7 (p < 0.05) and day 9 (p < 0.01) post‐insemination in conceived CVM carrier cows when compared with that in control conceived cows. The mean progesterone concentration during early pregnancy was significantly lower (p < 0.05) in conceived cows with CVM than that of control cows in the same period. However, the mean progesterone concentration did not differ significantly (p = 0.072) in CVM cows that showed fertilization failure or embryonic death than that of control cows. Additionally, of 13 conceived control cows, eight cows (61.5%) showed normal luteal function. In contrast, of nine conceived CVM cows, only four cows (44.4%) showed normal luteal function. The conception rate was 47.4% in CVM carrier cows and 61.9% in control cows, but this difference did not reach significance. In conclusion, progesterone concentration might be lowered during early pregnancy in conceived CVM cows compared with that in control cows.     

Population of Follicles and Luteal Structures during the Oestrous Cycle of Mares Detected by Three-Dimensional Internal Structure Microscopy

The structure of the equine ovary is different from that of other mammals in its extremely large size, the presence of ovarian fossa and the inverted location of its cortex and medulla. A three-dimensional internal structure microscopy (3D-ISM), which consists of a computer-controlled slicer, a CCD camera, a laser disc recorder and a PC, is very useful for the observation of the internal structures in equine ovaries. In addition, the three-dimensional images of follicles and corpus luteum (CL) reconstructed by the segmentation technique can clarify the spatial arrangement in the equine ovary. In this study, to understand the changes in the ovarian internal structures of the mare during the oestrous cycle, the size and numbers of follicles and luteal structures were analysed by 3D-ISM in addition to the concentrations of progesterone (P₄) and oestradiol-17β. As a result, many small follicles (<10 mm in diameter) were detected. It was recognized that the luteal structures were distinguished into three types, such as the corpus haemorragicum (CH), which is formed by blood elements at the cavity after ovulation, CL and corpus albican (CA). There were some CHs and CL in the group, which had the concentration of P₄ > 1 ng/ml. CHs were also observed in the group, which had low level of P₄ (P₄ < 1 ng/ml). CAs were found regardless of the P₄ level. In conclusion, 3D-ISM enabled the internal observation of the ovarian structures in detail, and estimation of the stage of the ovarian cycle with complementary physiological information. The findings by 3D-ISM provide basic information for clinical applications.     

Effects of Cholesterol on Progesterone Production by Goat Luteal Cell Subpopulations at Two Different Stages of the Luteal Phase

The aim of the present study was to evaluate the effects of cholesterol on progesterone production during long‐term culturing of luteal cell subpopulations at early and late luteal stages of the goat corpora lutea. Corpora lutea were collected from Angora goats on days 5 and 15 of the oestrous cycle. Luteal cells were isolated by collagenase digestion. The cells were separated into two distinct subpopulations by Percoll density‐gradient centrifugation. Both subpopulations of luteal cells staining positively for 3β‐HSD activities (5 × 10⁴ cell/well) were cultured with or without 22(R)‐hydroxycholesterol (22R‐HC) in serum‐free culture medium for periods of up to 7 days. Cells were incubated with serum (10%) for the first 18 h of incubation followed by serum‐free medium. Cell treatment (10 and 20 μg/ml) was performed on days 1, 3 and 5. Treatment of cells with both concentrations of 22R‐HC resulted in significant (p < 0.01) and dose‐dependent stimulation (p > 0.05) on progesterone production in both fractions of cells throughout 7 days of incubation. Treatment of the cells with cholesterol resulted in 2.5‐ and 9.0‐fold increases in progesterone accumulation on day 3 of incubation. Steroid production was maintained throughout the incubations when cells are incubated in serum‐free media treated with cholesterol and ITS premix. Cells collected from higher density of percoll layers produced 2.82 and 2.32 times more progesterone, in comparison to the lover density percoll layer, on days 5 and 15 of the oestrous cycle in untreated cell groups, respectively. Progesterone accumulation was decreased as incubation time advanced in all groups of untreated cells. These results demonstrated that goat luteal cell subpopulations secrete substantial amounts of progesterone in response to cholesterol treatment at least for 7 days, and cholesterol is required as progesterone precursor for maintaining a high‐level steroidogenesis during long‐life culturing of both cell subpopulations.     

Relationship between Ultrasonographic Assessment of the Corpus Luteum and Plasma Progesterone Concentration during the Oestrous Cycle in Monovular Ewes

Ultrasonographic observations of the corpus luteum (CL) and collection of blood samples for progesterone radioimmunoassay were performed daily during 15 oestrous cycles in Spanish Merino ewes, a consistently monovular breed. Ultrasonographic image of the CL changed during the oestrous cycle, increasing its echogenic pattern from ovulation to luteolysis. The size of the CL and mean progesterone levels were significantly affected by day of cycle (p < 0.05 and p < 0.001, respectively). Both increased their values from day 1 to day 12 (from 49.6 ± 7.4 to 154.6 ± 11.8 mm² and from 0.2 ± 0.0 to 2.8 ± 0.5 ng/ml, respectively) and then declined sharply until day 0 (28.2 ± 5.3 mm² and 0.1 ± 0.0 ng/ml, respectively). There was a significant correlation between CL area and plasma progesterone concentrations during the entire oestrous cycle, taking the developing and regressing phases of the CL separately (p < 0.05). A central cavity was observed in 33.3% of the CL studied. The presence of this cavity had no effect in total luteal‐tissue area of the CL nor on oestrous cycle length or on progesterone concentrations. Likewise, the cavity did not affect the correlations observed between CL size and progesterone levels, CL size and day of cycle and progesterone levels and day of cycle. It is concluded that ultrasonographic assessment of CL area is a reliable method for estimating peripheral plasma progesterone levels, regardless to the presence or absence of a cavity in the CL.     

Lysophosphatidic Acid Synthesis and its Receptors’ Expression in the Bovine Oviduct During the Oestrous Cycle

Lysophosphatidic acid (LPA) is a naturally occurring simple phospholipid which in the bovine reproductive system can be produced in the endometrium, corpus luteum, ovarian follicle and embryo. In this study, we examined the possibility that LPA receptors are expressed, and LPA synthesized, in the bovine oviduct. We found that the concentration of LPA was highest in infundibulum in the follicular phase of the oestrous cycle and was relatively high during the early‐luteal phase in all examined parts of the oviduct. We also documented that LPA synthesis engages both available pathways for LPA production. The autotaxin (ATX) protein expression was significantly higher in the infundibulum compared to the isthmus during the follicular phase of the oestrous cycle. During the early‐luteal phase of the oestrous cycle, ATX and phospholipase A2 (PLA2) protein expression was highest in ampulla, although the expression of LPARs was not as dynamic as LPA concentration in the oviduct tissue, and we presume that in the bovine oviduct, the most abundantly expressed receptor is LPAR2. In conclusion, our results indicate that the bovine oviduct is a site of LPA synthesis and a target for LPA action in the bovine reproductive tract. We documented that LPAR2 is the most abundantly expressed in the bovine oviduct. We hypothesize that in the bovine oviduct, LPA may be involved in the transport of gametes, fertilization and cellular signalling between the oviduct and cumulus–oocyte complex.     

Impact of Exogenous ACTH During Pro-Oestrus on Endocrine Profile and Oestrous Cycle Characteristics in Sows

Sows housed in freely moving groups have elevated cortisol levels until the rank order is established, which takes place within approximately 48 h. The aim of this investigation was to study the effect of repeated administration of synthetic adrenocorticotropic hormone (ACTH; Synacthen Depot), during the follicular phase (pro-oestrus) on oestrus, ovulation and endocrine parameters. Four multiparous sows were used. Follicular growth and ovulation were recorded by ultrasonography. The first oestrous cycle after weaning was used as control cycle. Onset of oestrus in the sow occurs 3-4 days after the time when plasma progesterone reaches a concentration of 8 nmol/l. The progesterone profile in the control cycle of the individual sow was used for estimation when the ACTH injections should start. In the third pro-oestrus ACTH (2.5 microg/kg) was given via an indwelling catheter every 2 h for 48 h. The sows were euthanased 4-6 days after onset of the third oestrus and the ovaries were examined. Cortisol levels were elevated during the treatment period (p < 0.05). The second cycle, in which the sows were injected with ACTH, was prolonged with 2.5 days compared with the control cycle (p < 0.05). The oestradiol pattern during oestrus was similar in the control and the treatment cycle in ovulating sows. Three sows had ovulated (fresh corpora lutea), but the ovaries contained additionally one or several luteinized follicles/cysts. In conclusion, ACTH administration during pro-oestrus caused a prolongation of the oestrous cycle and a disturbed follicular development.     

In vitro Release of Ovarian Progesterone is Decreased During the Oestrous Cycle and Pregnancy of Swine with Obesity/Leptin Resistance

Previous studies indicate that reproductive prolificacy of obese swine breeds is markedly influenced by embryo losses in early pregnancy. In such period, adequate secretion of progesterone (P4) by the ovary is essential for pregnancy success. This study analyses the luteal functionality during the oestrous cycle and early pregnancy of Iberian sows and Large White x Landrace females, in terms of P4 secretion after in vitro culture of luteal tissue stimulated or not with luteinizing hormone (LH). The secretion of progesterone (expressed in ng/mg of luteal tissue or ng/mgLT) of the corpora lutea of obese Iberian swine was always hampered when compared to lean genotypes, either during early oestrous cycle (110.7 ± 37.8 vs 259.7 ± 10.2 ng/mgLT; p < 0.0001), late oestrous cycle (49.0 ± 3.5 vs 75.92 ± 7.14 ng/mgLT; p < 0.0001) or early pregnancy (38.4 ± 2.1 vs 70.7 ± 5.3 ng/mgLT; p < 0.0001). The differences in basal P4 secretion remained after stimulation with LH. Finally, P4 secretion during early pregnancy of Iberian sows decreased with age and, hence, with obesity features (46.6 ± 4.2 vs 65.5 ± 4.8 ng/mgLT; p < 0.001). In conclusion, the results of the present study provide convincing evidence of a reduced luteal function during oestrous cycle and early pregnancy of sows with obesity/leptin resistance like Iberian sows, which may contribute to the low reproductive efficiency reported in this breed.     

白香猪发情周期外周血清P4、E2和LH含量的变化

用放射免疫分析法(RIA)测定了10头白香猪发情周期外周血清孕酮(P4)、17β-雌二醇(E2)和促黄体素(LH)含量的变化。血清孕酮的含量,在发情周期的第2d逐渐升高,峰值为21.25ng/ml±2.00ng/ml;E2含量的变化较特殊,在发情当天出现一个峰值,但最高值却出现在发情周期的第11d～13d,为79.48pg/ml±10.77pg/ml;促黄体素的含量在发情当日达到最高值以后逐渐下降。     

Changes of Connexin43 Expression in Non‐pregnant Porcine Myometrium Correlate with Progesterone Concentration During Oestrous Cycle

Connexin43 (Cx43) is a major protein of myometrial gap junctions. The number of Cx43 gap junctions increase dramatically with the onset of labour in association with development of synchronized uterine contractions. The formation of myometrial gap junctions follows an increase in the oestrogen to progesterone ratio indicating an important role of steroid hormones in regulating Cx43 expression at term. However, no relationship has been established between the expression of Cx43 in the non‐pregnant myometrium and concentration of steroid hormones during the oestrous cycle. Here, we used immunofluorescence and Western blotting to analyse the expression of Cx43 gap junctions in the myometrium of pre‐pubertal pigs (n = 7) and mature pigs at pre‐ovulatory (n = 7), luteal (n = 5) and late luteal (n = 3) stages of the oestrous cycle. The number of Cx43 gap junctions calculated per 1 mm² of the myometrial section was low in pre‐pubertal pigs and significantly higher (p < 0.022) in pre‐ovulatory animals. In relation to pre‐ovulatory animals the number of myometrial gap junctions was significantly lower (p < 0.019) at the luteal phase and correlated with significantly higher (p < 0.005) concentration of endogenous progesterone. Phosphorylated isoforms of Cx43 protein were expressed in the myometrium of pre‐pubertal pigs and mature animals at pre‐ovulatory and late luteal phases, while they were down regulated at the luteal stage. These results indicate that changes of Cx43 expression in the porcine myometrium during the oestrous cycle may be regulated by progesterone concentration and may contribute to the modulation of uterine motility.     

Histological Study of Canine Mammary Gland During the Oestrous Cycle

The development of the mammary gland is a puzzling phenomenon and the research on this field has been focussed mostly on the carcinogenesis, with a less goal‐oriented concern in basic histology. In order to determine the histological features of normal mammary gland in the different oestrous phases we used 39 non‐pregnant female dogs of various breeds and ages. The animals were grouped in: pre‐pubertal, pro‐oestrous, oestrous, early and late dioestrous, early and late anoestrous phases. Major changes of the canine mammary histology throughout the oestrous cycle were identified in this study. A rudimentary gland with few ducts in the base of the nipple was observed in pre‐pubertal female individuals and pubertal pro‐oestrous female ones. In the oestrus, small inactive lobules associated with ductal branching and inconspicuous regressive changes were observed, while in early dioestrus, a ductal arborization was present. In late dioestrus, a complete lobuloalveolar differentiation and secretory capacity was achieved. The regressive histological features were abundant on early anoestrus, and markedly generalized on late anoestrus. The regressive process was longer in the more caudal gland pairs. This work provides baseline knowledge of canine mammary gland that may be relevant for interspecies comparative purposes and for pathologists dealing with mammary gland tumours.     

Immunohistochemical Detection of Receptors for Oestrogen and Progesterone in Endometrial Glands and Stroma during the Oestrous Cycle in Nelore (Bos taurus indicus) Cows

The aim of the present study was to monitor endometrial distribution and concentrations of oestrogen receptors α (ERα) and progesterone receptors (PR) by immunohistochemistry in Nelore cows (Bos taurus indicus) during the oestrous cycle. Blood samples were collected for progesterone measurement and endometrial samples were taken from the uterine horn contra lateral to the corpus luteum in 16 cows at days 0 (ovulation), 5, 9, 13 and 19 of the oestrous cycle. Immunostaining evaluation for ERα and PR in the glandular epithelium and uterine stroma was performed by two methods: positive nuclei counting and staining intensity of the nuclei. Specific positive staining reactions for both receptors were limited to cell nuclei and they were not identified in the cytoplasm. The proportion of ERα positive nuclei had a temporal variation throughout the oestrous cycle in both cell types evaluated and was higher in uterine stroma than the glandular epithelium (p < 0.05). The greatest proportion of ERα stained nuclei was observed at oestrus and during the initial and mid luteal phase (days 5, 9 and 13) (p < 0.05) in the glandular epithelium and at days 0, 5 and 9 in the uterine stroma (p < 0.01). The proportion of PR positive nuclei remained constant throughout the entire oestrous cycle for both cell types evaluated (p > 0.05). A higher proportion of PR positive nuclei was measured in the uterine stroma compared with the glandular epithelium (p < 0.05). Intensity of staining for ERα and PR varied throughout the oestrous cycle (p < 0.01). There was a higher staining intensity at days 0 and 5 in the stroma for ERα (p < 0.01) and PR (p < 0.01) and in the glandular epithelium at days 0, 5, 9 and 13 for ERα (p < 0.01) and at days 0, 5 and 9 for PR (p < 0.01) when compared with the other evaluated days. These data demonstrate that ERα and PR expression varied throughout the oestrous cycle in Nelore cows, in general with highest concentrations at oestrus and the lowest during the luteal phase. This is similar to patterns observed in Bos taurus taurus.     

Variations of Equine Urinary Volatile Compounds during the Oestrous Cycle

Ma, W. and Klemm, W.R., 1997. Variations of equine urinary volatile compounds during the oestrous cycle. Veterinary Research Communications, 21 (6), 437-446Equine urine was analysed by capillary gas chromatography. The volatile profiles from oestrous and dioestrous samples were compared to establish any qualitative or quantitative difference that may have potential value in olfactory communication. Forty-five different volatile compounds were detected. Of these, 17 major compounds were common to all chromatograms. The chemical profile of oestrous urine was distinguished by the presence of a unique peak that was not present in dioestrous samples. Numerous constituents exhibited endocrine dependence: while the concentrations of seix peaks increased at oestrus, the concentrations of another five peaks decreased at the same time. Since oestrous urine, but not dioestrous urine, has been shown to elicit sexual behaviour in the stallion, the unique peak, together with the peaks that were present in increased concentrations at oestrus, may represent important chemical signals that stallions use to detect urinary oestrous odours. Statistical analyses also indicated that the relative ratios (normalized peak areas) of many peaks changed significantly across the oestrous cycle: the ratios increased in nine peaks, decreased in six peaks, and remained constant in two peaks at oestrus.     

Seasonal Changes in Luteal Progesterone Concentration and mRNA Expressions of Progesterone Synthesis-related Proteins in the Corpus Luteum of Mares

Although circulating progesterone (P(4)) levels tend to change with the season, little is known about the seasonal changes of P(4) synthesis-related proteins in the corpus luteum (CL) of mares. To examine these changes, seventy-four ovaries containing a CL were collected from Anglo-Norman mares at a local abattoir in Kumamoto, Japan (~N32°), five times during one year. The stages of the CLs were classified as early, mid and regressed by macroscopic observation of the CL and follicles. The mid CL, which had the highest P(4) concentration, was used to evaluate the seasonal changes in P(4) synthesis. The luteal P(4) concentration and mRNA expression of luteinizing hormone receptor (LHCGR) were lowest during early winter and highest during late winter. The mRNA expressions of steroidogenic acute regulatory protein (StAR), P450 cholesterol side-chain cleavage enzyme (P450scc) and 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD) were lowest during early winter and increased during late winter. These results suggest that P(4) synthesis in the CL is affected by the seasonal changes in the mRNA expressions of P(4) synthesis-related proteins in mares.